1. Field of the Invention
The present invention relates to a method for forming quantum dots using a metal thin film or metal powder, and more particularly to a method for forming nanometer-sized metal oxide quantum dots which can easily control the size, density and uniformity of the oxide quantum dots.
2. Description of the Related Art
In general, materials having a particle size less than several tens of nanometers may exhibit new physical properties such as quantum effects. Quantum dots refer to physical subunits exhibiting these quantum effects.
Conventional methods for forming quantum dots have been achieved by one of the following various processes, for example: (i) a process including forming quantum dots on a selected substrate depending on the position of quantum dots to be formed, and growing the quantum dots thereon [e.g., InAs is grown on a GaAs substrate and InAs is grown on an InP substrate]; (ii) a process for forming quantum dots inside a substrate or insulating thin film; (iii) a process including forming quantum dots on selected regions of a substrate, and covering a multi-layer thin film thereon; (iv) a process for controlling the size and distribution of particles and minimizing the coalescence of the particles by using sputtering, vacuum evaporation deposition, chemical vapor deposition, or epitaxy technique. In addition, this process can solve a variety of problems generated during the procedure; (v) an inert gas condensation using thermal evaporation obtained after vaporizing a precursor; (vi) a vapor phase synthesis using microwave plasma or laser ablation; (vii) a process using a chemical vapor condensation technique for decomposing and synthesizing a metal-organic material in combustion flame or a hot-wall reactor; (viii) a process for producing metals/alloys and ceramic nanometer-sized powders as well as coated or doped nano-composite powders at atmospheric pressure or under low vacuum using an aerosol-spraying technique, or a process for producing a material containing a large amount of narrowly density-distributed nanoparticles by directly spraying onto a substrate; (ix) a chemical process for preventing the coalescence of fluorescent particles by granulating precursor particles using a nucleation technique and growing the precursor granules. This process is carried out by mixing an aqueous solution of fluorescent raw materials and an aqueous solution of a compound containing a luminescent metal in the presence of a solvent, precipitating particles from the mixture, heating the precipitated particles together with vapor phase fluorescent raw materials to produce fluorescent nanoparticles.
However, these conventional processes for forming quantum dots have problems that the distributed state of particles and the thickness of layers cannot be readily controlled and the processes undergo many complex steps, causing reduced throughput and considerable production cost.
In particular, according to the chemical approaches among these conventional methods, nanoparticles manufactured by injecting an aqueous solution or spray solution are condensed, sintered and annealed. At this time, bulky particles are formed. Accordingly, the chemical approaches require additional catalysts and additives to prevent the nanoparticles from coalescing. Moreover, the chemical approaches are disadvantageous in terms of low yield. Furthermore, when a powder is mixed with a polymer to produce a polymer containing nanoparticles, the powder must be previously manufactured to a nanometer size.